1. Field of the Invention
The present invention relates to ink jet recording apparatuses, and in particular, to ink jet recording apparatuses provided with the function of reducing the reflected light of ultraviolet rays emitted from an ultraviolet ray emitting apparatus.
2. Description of the Related Art
Conventionally, ink jet recording apparatuses have been known as recording apparatuses that can print on various types of recording media typified by ordinary copying paper. An ink jet recording apparatus is a recording apparatus that forms images on the recording medium by emitting ink, which is the color material, directly onto the recording medium from nozzles provided on the surface of the recording head that is facing the recording medium, and making the ink land on, penetrate or get fixed onto the recording medium, and has excellent features in terms of the simplicity of the process, quietness during printing, and the quality of printing and printed images.
Recently, in ink jet recording apparatuses, there are situations in which image recording is done using as the recording medium various types of materials such as plastic or metal that do not have ink absorption capacity, and in such situations, in order to fix the ink on such recording media, it is very common to use photo-hardening type ink. Usually, in an ink jet recording apparatus using such photo-hardening type ink, an ultraviolet light radiating unit would have been installed in the apparatus for hardening the ink, and at the time of recording images on the recording media, immediately after causing the ink to land on the recording medium, the ink is hardened and fixed by irradiating the ink with ultraviolet light from a light source provided in the ultraviolet light radiating unit under some constant conditions enabling hardening of the ink such as the duration of radiation and number of times of irradiation.
As an ink jet recording apparatus provided with an ultraviolet light radiating unit described above, an ink jet recording apparatus 101 has been developed such as the one shown in FIG. 4 and FIG. 5. This ink jet recording apparatus 101 is provided with an ultraviolet light radiating unit 102 and a recording head 103 that can move freely in the left-right direction in FIG. 4 and FIG. 5 (hereinafter referred to as the main scanning direction X), and the ultraviolet light radiating unit 102 moves in the main scanning direction X in combination with the movement of the recording head in the left-right direction.
However, when the ultraviolet light radiating unit 102 is placed at the home position A shown in FIG. 4 or the head movement direction changing position B shown in FIG. 5, that is, at a position at which it is not placed opposite the top surface of the platen 104, there was the problem that the reflected light of the ultraviolet light emitted from the ultraviolet light radiating unit 102 is irradiated onto the nozzle of the recording head 103, thereby causing the ink accumulated in the recording head 103 to get hardened.
In view of this, as a ink jet recording apparatus in which it is possible to prevent the clogging of the ink path of the recording head 103 due to hardening of the ink, as is shown in FIG. 6, an ink jet recording apparatus 111 has been developed (see, for example, Patent Document 1) in which plate members 105 and 106 that prevent reflection of ultraviolet light towards the recording head 103 have been placed in the regions of the home position A and the head movement direction changing position B so that they are in close contact with the bottom surface of the ultraviolet light radiating unit 102.
Further, in the case of an ink jet recording apparatus using photo-hardening type ink, because the ultraviolet light emitted from the ultraviolet light radiating unit was getting reflected at the top surface of the platen after the recording medium had passed and was irradiated on the emitting surface of the recording head, any ink or ink mist adhering to the nozzle was getting hardened. Because of this, there was the problem that the ink emitting ability was getting reduced and it was difficult to reproduce images in a stable manner.
Therefore, as an ink jet recording apparatus capable of reproducing high resolution images in a stable manner, an ink jet recording apparatus has been developed (see, for example, Patent Document 2), in which an ultraviolet light absorption section has been formed by coating an ultraviolet light absorbing material that includes an organic material (hereinafter referred to as an organic ultraviolet light absorbing material) on the top surface of the platen.
Patent Document 1: Japanese Unexamined Patent Application Open to Public Inspection No. 2004-338264.
Patent Document 2: Japanese Unexamined Patent Application Open to Public Inspection No. 2003-276256.
Here, in the case of the ink jet recording apparatus 111 disclosed in Patent Document 1 as described above, the purpose is to prevent the reflected light of the ultraviolet light emitted from the ultraviolet light radiating unit 102 placed at a position that is not opposite to the platen 104.
However, as is shown in FIG. 7, in case the ultraviolet light radiating unit 102 is placed at a position opposite to the platen 104, since the height of the gap S formed below the recording head 103 changes depending on the thickness of the recording medium P supported by the platen 104, when a rigid base material such as a plate material with a large thickness is used for the recording medium P, the height of the gap S is widely different when compared at a position above the rigid base material and at a position away from the base material.
Therefore, if the ultraviolet light radiating unit 102 is placed at a position above the surface of the platen 104 and separated from the rigid base material, there was the problem that the ink or ink mist adhered to the nozzle of the recording head 103 was likely to get hardened because of the increase in the amount of light radiated onto the recording head 103 by the radiated ultraviolet light after being reflected from the top surface of the platen 104 due to the increase in the height of the gap S.
On the other hand, in the case of the ink jet recording apparatus disclosed in Patent Document 2 as described above, although the ultraviolet light passing through the recording medium is absorbed by the ultraviolet light absorbing section provided on the platen, however, because the organic ultraviolet light absorbing material forming the ultraviolet light absorbing section gets dissociated due to irradiation with ultraviolet light, there was the problem that the ultraviolet light absorption effect in the ultraviolet light absorption section decreased substantially.
The present invention was made considering the points mentioned above, and the purpose of the present invention is to provide an ink jet recording apparatus that can prevent the hardening of the ink or ink mist adhered to the nozzle even when the thickness dimension of the recording medium is large.